title: Photocatalytic generation of multiple ROS types using low-temperature crystallized anodic TiO₂ nanotube arrays.
abstract: This study investigates the photocatalytic efficiency, type of reactive oxygen species (ROS) produced, and potential for structural and morphological modification of anodic TiO₂ nanotubes (NTs) synthesized using a novel, energy efficient, low temperature crystallization process. These TiO₂ NTs show greater photocatalytic efficiency than traditional high-temperature sintered NTs or supported Degussa P25 TiO₂, as measured by degradation of methyl orange, a model organic dye pollutant. EPR analysis shows that low-temperature crystallized TiO₂ NTs generate both hydroxyl radicals and singlet oxygen, while high-temperature sintered TiO₂ NTs generate primarily hydroxyl radicals but no singlet oxygen. This "cocktail" of reactive oxygen species, combined with an increased surface area, contributes to the increased efficiency of this photocatalytic material. Furthermore, variation of the NT crystallization parameters enables control of structural and morphological properties so that TiO₂-NTs can be optimized for scale-up and for specific treatment scenarios.
authors.affiliation: Electronic Materials Research Laboratory, School of Electronic and Information Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, China.
authors.forename: Yulong
authors.initials: Y
authors.lastname: Liao
authors.forename: Jonathon
authors.initials: J
authors.lastname: Brame
authors.forename: Wenxiu
authors.initials: W
authors.lastname: Que
authors.forename: Zongming
authors.initials: Z
authors.lastname: Xiu
authors.forename: Haixia
authors.initials: H
authors.lastname: Xie
authors.forename: Qilin
authors.initials: Q
authors.lastname: Li
authors.forename: Marian
authors.initials: M
authors.lastname: Fabian
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Alvarez
mesh_terms: D001391:Azo Compounds / Q000737:chemistry; D002384:Catalysis; D003460:Crystallization; D004578:Electron Spin Resonance Spectroscopy; D055772:Green Chemistry Technology; D015386:Hazardous Substances; D017665:Hydroxyl Radical; D008422:Materials Testing; D036103:Nanotechnology / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry*; D055668:Photochemical Processes; D017382:Reactive Oxygen Species / Q000737:chemistry*; D026082:Singlet Oxygen; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D062065:Wastewater; D014874:Water Pollutants, Chemical / Q000737:chemistry; D018508:Water Purification / Q000379:methods
chemical_list: D001391:Azo Compounds; D015386:Hazardous Substances; D017665:Hydroxyl Radical; D017382:Reactive Oxygen Species; D026082:Singlet Oxygen; D014025:Titanium; D062065:Wastewater; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; C100258:methyl orange
keywords: Crystallization; Green synthesis; Nanotubes; Photocatalysis; Reactive oxygen species; TiO(2)